: Been awhile since we heard of someone leaving, did anybody else leave this
: year since Chris Buckley?

As alluded to in the tweet, he was a campaign designer. I believe he did parts of Composer, at the least, which is probably the best Halo 4 mission and one of the better Halo campaign levels in general to me.

Don't think we've seen that many departures as of recent; most people left or got staffed up after Halo 4 shipped. I imagine there would be less turnover in the middle of a big new project.